1. Field of the Invention
The present invention relates to the field of apparatus used to modify the impact of waves as they wash ashore and diminish the impact of the waves in eroding beaches and other shoreline property. Diminishing beaches due to wave action and/or current erosion and lack of sediment replenishment from rivers are the primary cause of the threat to shoreline structures from storm tides, currents and wave action.
2. Description of the Prior Art
Historically, artificial reefs have been used to some degree of success in mitigating wave and tidal damage to shoreline structures. However, artificial reefs are typically extremely expensive to build and have short life spans.
Artificial reefs typically encourage ocean waves to expend their energy by breaking offshore, thereby reducing the impact of wave energy on the shoreline. Artificial reefs can be used to encourage sediment accretion in specific areas although present art is inexact for this purpose.
Present art used in the design and construction of artificial reefs almost universally incorporate monolithic design features. These include geo-textile sand bags, sunken boats or ships, rip rap or dredged materials.
Existing Art:
Weight, Buoyancy, Permeability and Flexibility:
Weight:
Present art depends on mass to keep an artificial reef in place. Massive weight requires unnecessary effort and cost in the form of material expense and handling costs. Massive weight also becomes a liability on sand or mud bottoms. The nature of sand and mud bottoms can best be described as solid fluids. Any device or object placed on the sea floor which has greater density than the “fluidized solid” bottom will eventually sink. This is one of the most common failures in artificial reefs using present art. Conversely, any device or object which has a density less than the “fluidized solid” bottom will “float” indefinitely.
Surface Area:
Monolithic structures by nature have relatively small surface areas relative to weight. Relatively small surface area decreases the overall effect on wave formation, littoral current dissipation and energy absorption, all of which require large surface areas.
Monolithic, small area structures used in the present art have an inability to disperse or absorb energy acting on the structure in the form of waves and/or currents. Littoral currents (currents moving parallel to shore) represent the main force that moves sediment and produces scouring along objects on the sea floor. Monolithic structures are able to redirect a current's energy. The result of energy re-direction is a change in speed and direction of current movement along with the sediment it carries. This is contrary to the ideal result which is: current energy absorption and sediment accretion within the reef structure.
Permeability:
Present artificial reef art with its monolithic nature and relatively small surface areas are not permeable. They do not let currents carrying sediment pass through the structure. Monolithic structures tend to redirect and increase the speed of littoral currents which allow them greater sediment carrying capacity. This result is directly contrary to the desired effect which is to encourage sediment accretion in specific areas especially within the reef's structure.
Flexibility:
Present art using monolithic structures depending on mass and relatively small surface areas are designed to redirect energy rather than absorb it. These are typically rigid structures subject to concentrated loads or forces. Nature demonstrates that flexibility is a key quality for energy absorption and structure longevity in an ocean environment. Present art does not include this key quality.
One of the present inventors, Gary Ross, is the inventor of the “Artificial Surfing Reef” which was patented on May 4, 1993 and assigned U.S. Pat. No. 5,207,531. The purpose of that invention was to create surfing waves. The invention included stacked groups of elongated pipes.
There is a significant need for an improved structure which will serve to modify the impact of waves as they wash ashore and diminish the impact of the waves in eroding beaches and other shoreline property.